“Why did the blonde climb up to the roof of the bar?” (joke)

Drinks that are “on the house” are free, and there’s a classic joke:
 
Q: Why did the blonde climb up to the roof of the bar?
A: She heard that the drinks were on the house.
 
The joke became popular with a series of “moron” jokes in 1943. The moron either would “bring a ladder into the bar” or “climb up to the roof of the bar.” The “moron” was replaced by a “blonde” in the joke since at least the 1990s.
 
     
2 April 1923, Sandusky (OH) Star-Journal, “Tom Sims Says,” pg 12, col. 3:
When an airplane loaded with booze landed on a Maine farmer’s roof the drinks were on the house.
 
26 March 1943, The Twig (Meredith College, Raleigh, NC), “The Little Moron,” pg. 2, col. 4:
Have you heard about the little moron who took a ladder to the party because he heard that the drinks were on the house?
 
25 April 1943, Dallas (TX) Morning News, “Younger Set Now Doing It: Gag Writing” (UP), sec. 4, pg. 5, col. 8:
It might be “Have you heard about the moron who climbed to the top of the roof because he heard that the drinks were on the house?” ...
 
1 May 1943, Sheppard Field (TX) Texacts, “Squadron Squibs,” pg. 9, col. 1:
Pvt. George Morrison appreciates good jokes—Did you ever hear the one about the little moron who always carried a ladder with him? Yep, he heard the drinks were on the house! Ouch! Don’t twist my arm! I quit on that one!
 
13 May 1943, Portsmouth (OH) Times, “Morons” by Damon Runyon, pg. 6, col. 7:
“Went to the roof because he heard ihe drinks were on the house.”
     
16 May 1943, Bluefield (WV) Daily Telegraph, “Down Sports Trail Into The Press Box” with Stubby Currence, sec. 2, pg. 2, col. 2:
The office moron says the reason the Scotchman took a ladder to the party at a friend’s was because he heard the drinks were on the house.
 
Google Books
The New Yorker
Volume 30, Part 1
1954
Pg. 93:
“Why did the moron look for his cocktail on the roof?”
(...)
“Because they told him the drinks were on the house,” he said.
   
Google Books
New York Folklore Quarterly
Volume 11
1955
Pg. 212:
Why did the moron go up on the roof? A
ns.— He heard the drinks were on the house.
 
12 February 1965, San Diego (CA) Union, “Fun Time—THe RIddle Box,” pg. A26, col. 2:
Why did the cowboy brin a ladder to the saloon
Because he heard the drinks were on the house.
 
Google Books
How to Eat Like a Child, and Other Lessons in Not Being a Grown-up
By Delia Ephron
New York, NY: Viking Press
1978
Pg. 39:
Why did the little moron take a ladder to the party? Because he heard that drinks were on the house.
 
Google Groups: alt.life.sucks
Jokes for you
Peterk
8/4/98
(...)
Q: Why did the blonde climb up to the roof of the bar?
A: She heard that the drinks were on the house!
     
Google Groups: alt.tv.space-a-n-b
A FEW GOOD MEN!!
Tony Soottinanchai
11/24/96
That was incredibly stupid. Who wrote this, a blonde?
(...)
>>Why did the Marine climb up to the roof of the bar…he heard that the
>>drinks were on the house.
 
Google BOoks
Jokes, Riddles and Wisdom:
The Best Collection Ever
By Roger Kuder
San Jose, CA: ToExcel Press
2000
Pg. 62:
Q: Why did the blonde climb up to the roof of the bar?
A: She heard that the drinks were on the house.
 
Google Books
John Heyman’s Book of Really Good Jokes:
A Lifetime of Laughs
Xlibris Corporation (Xlibris.com)
2011
By John A. Heyman
Pg. 19:
Why did the blonde climb onto the roof? Someone told her the drinks were on the house!
 
Twitter
Clean Jokes
‏@CleanJokes247
#CleanJokes Q: Why did the blond climb up to the roof of the bar? A: He heard that the drinks were on the house… http://ow.ly/39SXYw
10:33 PM - 8 Jan 2016